Withdrawal of $300 million comes before a visit by Secretary of State Mike Pompeo to Islamabad

WASHINGTON—The Pentagon said it suspended $300 million in military aid to Pakistan, accusing it of not doing enough to tackle militant groups, in a move certain to heighten tensions between the two countries ahead of Secretary of State Mike Pompeo’s visit this week to Islamabad.

The Trump administration made the decision to suspend the Coalition Support Fund earlier this year before a Sept. 30 deadline and the Pentagon confirmed the decision this weekend. The Pentagon said the U.S. military made the decision “due to a lack...